1. Field of the Invention
The present invention relates to an organic electroluminescence display device.
2. Description of the Related Art
In top-emission type organic electroluminescence display devices, light is extracted from a negative electrode, and thus the negative electrode is required to be high in light transmittance from the perspective of improvement of light extraction efficiency. Meanwhile, a negative electrode is also required to be high in conductivity from the perspective of low power consumption.
Transparent oxide semiconductor films are generally used as negative electrodes, but an increase in thickness of the transparent oxide semiconductor film is essential to reduce sheet resistance, and transmittance is reduced. Light transmittance and conductivity have a trade-off relationship with each other, and thus it is difficult to satisfy both of them.
When a combination of a transparent oxide semiconductor film and a metal thin film having high conductivity is used, the influence of a light interference effect by the reflection of a metal thin film is great, and thus it becomes difficult to adjust a luminescent color.
When a metal film having high conductivity is formed in a non-emission region, a pixel aperture is not reduced in size, but a higher film formation accuracy than that of the pixel aperture is required, and thus application in production is difficult. For example, it is possible to form a minute auxiliary wiring on a transparent conductive film by deposition using a shadow mask, but a film formation region becomes narrower than a pixel. Thus, a highly accurate mask manufacturing technique and film formation technique are required, which results in a difficulty in practical application.
JP 2002-33198 A or JP 2006-278241 A discloses that an organic layer and a negative electrode are formed on a thin film transistor (TFT) substrate, an adhesion layer is formed on an encapsulation substrate for encapsulating the organic layer, an auxiliary wiring is formed on the adhesion layer, and the encapsulation substrate is bonded to the TFT substrate so that the auxiliary wiring faces a negative electrode. Meanwhile, the auxiliary wiring is pushed into the adhesion layer, and thus the auxiliary wiring and the negative electrode come into contact with each other. In this example, since the auxiliary wiring is formed on the adhesion layer, there is a problem in that a material is limited for a reason that the formation has to be performed without thermal curing.
JP 2009-128671 A discloses that a transparent conductive film is formed on an encapsulation substrate, and the encapsulation substrate is bonded to a TFT substrate, thereby bringing the transparent conductive film into contact with a negative electrode on the TFT substrate. However, since the transparent conductive film covers an emission region, a decrease in light transmittance is inevitable.